abstract-ethan

Title: Kinetic Facilitation of interfaces in thin entangled polymer films Abstract: Amorphous polymeric materials are used in a wide array of technologies ranging from organic electronics to structural components of airplanes. As many of these technologies trend towards nanometer length scales, it is imperative to have a fundamental understanding of the properties of polymer glasses at the length scale, geometry, and environment of the application.

Recent work in polymer physics shows that the structural relaxation time near a free surface of a thin polystyrene film is significantly different from that of the bulk polymer. This can have a large influence on their properties. For instance, studies have shown that polystyrene thin films exhibit a decreased glass transition temperature (Tg) as the thickness decreases below 60 nm. A puzzling aspect of this phenomenon is that most studies indicate that there is no molecular weight dependence on Tg reduction in supported films, while the same phenomenon in freestanding polystyrene films shows a strong molecular weight dependence. In this study, we use cooling-rate dependent Tg measurements to indirectly probe the relaxation dynamics of thin polystyrene films, and show they are directly influenced by the dynamics of the free surface.

Furthermore, we show that the relaxation dynamics of supported polystyrene films slow down slightly as the molecular weight of polystyrene is increased.

Bio: Ethan Glor is a PhD candidate in chemistry at the University of Pennsylvania. His current work under Dr. Zahra Fakhraai consists of gaining new insight into the dynamics of amorphous polymeric materials in the hopes of eventually preparing polymeric glasses with high density and high kinetic stability. Ethan was awarded an Honorable Mention for the National Science Foundation Graduate Research Fellowship in 2013, and is a 2011 graduate of Haverford College with a BS in Chemistry.